Ball mill provided with an agitator

ABSTRACT

A ball mill is provided with an agitator and comprises a grinding chamber containing grinding medium, a stator and a rotor which are arranged in said grinding chamber, an input opening for material to be ground and an output opening for ground material which are used for bringing the material to be ground to the grinding chamber and for evacuating the ground material therefrom. The mill also comprises a device for separating the grinding medium arranged in the grinding chamber above the output opening. The rotor is embodied in the form of a rotational symmetry body, and the stator is formed by an internal surface which is complementary to the grinding chamber. The inventive rotor and the stator are provided with pins which are distributed through all surface thereof and projected to the grinding chamber.

The invention relates to an agitating ball mill according to thepreamble of claim 1.

Such agitating ball mills have a grinding chamber containing grindingmedia, a stator and a rotor, which are arranged in the grinding chamber,an input opening and an output opening for feeding and removing grindingmaterial to or from the grinding chamber, as well as a grinding mediumseparation device arranged in the grinding chamber upstream from theoutput opening, which is used to separate grinding media entrained inthe grinding material from the grinding material before the latter isremoved from the grinding space through the output opening.

Agitating ball mills are used in the area of foodstuffs and in themanufacture of fine particles down to the nanometer range in size.Particles or agglomerates suspended in a liquid are here conveyed intothe grinding chamber, and comminuted or dispersed in the grindingchamber by means of auxiliary grinding media before being conveyed outof the grinding chamber. To prevent the auxiliary grinding media frombecoming dragged out of the agitating ball mill by the liquid stream ofgrinding material during this wet grinding process, resulting in theloss of the agitating ball mill and contamination of the grindingmaterial, the auxiliary grinding media are held back in the grindingchamber by a separation device. A separating gap, grading screen orcellular wheel are used as separation devices. Essentially sphericalelements made out of steel, glass, ceramic or plastic are used as theauxiliary grinding media.

In order to increase the mechanical grinding power introduced into thegrinding material in the grinding chamber, the rotor and/or stator ofknown agitating ball mills is provided with pins that extend into thegrinding chamber. As a result, impacts between the grinding material andthe pins during operation directly contribute to the grinding power onthe one hand. On the other hand, an indirect contribution to grindingpower is made by impacts between the pins and the (auxiliary) grindingmedia entrained in the grinding material and subsequent impacts betweenthe grinding material and grinding media. Finally, the shear andexpansion forces acting on the grinding material also help comminute thesuspended grinding material particles.

The object of the invention is to achieve an enhanced grinding effectrelative to known agitating ball mils at a prescribed rotor/statorgeometry or grinding chamber geometry and at a prescribed rotor speed.

This object is achieved with the agitating ball mill according to claim1.

The fact that the rotor is essentially shaped like a rotationallysymmetric element and the stator is formed by an essentiallycomplementary inner surface of the grinding chamber enables a high powerdensity for the mechanical introduction of energy into the grindingmaterial as well as the greatest possible ratio between the processingarea space and processing area volume, and hence an optimal cooling ofthe grinding material during wet grinding or comminuting.

The fact that the rotor and stator have pins distributed over theirentire respective surface, extending from the respective surface andprojecting into the processing space enables the direct and indirectaction of the pins distributed over the entire grinding chamber volume,i.e., the impacts between the grinding material and pins, the impactsbetween the pins and the grinding media entrained in the grindingmaterial, as well as the shearing and expansion forces triggered by thepins in the suspension consisting of grinding material and grindingmedia, which together help comminute the suspended grinding materialparticles.

As a whole, then, improved grinding power is achieved, accompaniedsimultaneously by an evening out of grinding intensity, and hence alsoof an unnecessary strain on the grinding material, e.g., as the resultof local overheating, in the entire grinding chamber.

It is particularly advantageous for the grinding material input openingto be arranged in a radially outer area of the grinding chamber, and thegrinding material output opening to be arranged in a radially inner areaof the grinding chamber. During operation, an equilibrium essentiallysets in at on the auxiliary grinding media between a radially outwardlydirected centrifugal force component due to the rotation of the rotoraround its rotational axis and a radially inwardly directed drag forcecomponent due to the grinding material flowing radially from the outsidein. The flow of grinding material is maintained by a separate pump, forexample. This exposure to centrifugal force provides a “dynamic” relieffor the separation device situated radially inside the grinding materialoutput opening, i.e., most of the auxiliary grinding media is suspended,more or less stationary, in the radially outer areas of the processingarea, and forms a “swarm” of auxiliary grinding media through which thegrinding material is pumped. The few auxiliary grinding media that getinto the radially inner area of the processing area in the process arethen caught by the separation device. As a result, the separation deviceis protected and subjected to less wear.

The rotor can essentially be shaped like a truncated cone, wherein thegrinding material input opening is arranged in the area of the widetruncated cone end, and the grinding material output opening is arrangedin the area of the narrow truncated cone end of the grinding chamber. Asan alternative, the rotor can also essentially be shaped like a doubletruncated cone. In both cases, the grinding material is preferablypumped radially from the outside radially inward.

As a further alternative, the rotor can essentially be shaped like acylinder, wherein the grinding material input opening is arranged in thearea of the first cylinder end, and the grinding material output openingis arranged in the area of the second cylinder end of the grindingchamber, and the grinding material is essentially spirally transportedalong the cylinder jacket of the rotor through the processing area.

In another advantageous embodiment, the rotor is essentially shaped likea disk, wherein the grinding material input opening is arranged in theradially outer peripheral area, and the grinding material output openingis arranged in the radially inner axial area of the grinding chamber, sothat the grinding material again flows through the processing area fromthe outside in. Here as well, the aforementioned equilibrium between acentrifugal force component and drag force component is also establishedat the auxiliary grinding media during operation. The grinding materialpumped from outside in then once again provides the “dynamic” relief forthe radially inner separation device.

It is particularly advantageous for the disk-shaped rotor to have pinson both its two flat disk surfaces and not its peripheral surface. Theradially most outwardly lying pins are the fastest of all pins duringoperation. Since most of the auxiliary grinding media are radiallysuspended outside, a significant portion of the grinding effect isexerted in just this peripheral area of the processing area alone,resulting in a clearly increase in grinding power at the disk edge bycomparison to an agitating ball mill without pins.

The grinding chamber with its stator and rotor and the separation devicecan preferably be pivoted into a swiveled position in such a way thatthe separation device arrives at a high location, which is preferablyhigher than most of the entire grinding chamber volume. This makes itpossible to remove the separation device without evacuating theauxiliary grinding medium or product, since the auxiliary grindingmedium swell does not reach the height of the separation device in theswiveled position. In addition, this allows the use in the agitatingball mill of a rotatable separation device with spoke or leaf-likeelements, e.g., a spoke wheel, paddle wheel or cellular wheel, whereinthe separating effect of the separation device only comes about when itstarts to rotate. Because the processing zone can swivel according tothe invention, the separation device can be made operational in thiscase, as long as the processing zone is tilted, and the separationdevice is situated at the high location. After activation, theprocessing zone is then tilted to the operational setting, in which theauxiliary grinding media now arrive at the separation device, which nowexerts a separating action.

Once between 50% and 100% of the entire grinding chamber volume liesunder the separation device in the swiveled position, depending on thegrinding medium quantity in the agitating ball mill, no auxiliarygrinding media will be able to fall out of the grinding chamber owing tothe use of a “rotatable” separation device that is inactive when idle,or the lack of a dismantled separation device.

The swiveled, high location of the separation device is best the highestlocation of the agitating ball mill achievable via swiveling. Thisfacilitates access to the separation device. In addition, auxiliarygrinding media located in or on the separation device can be poured outor stripped into the grinding chamber without any problem via theopening to the grinding chamber during the dismantling of the separationdevice.

The swiveling position is best a non-operating position of the agitatingball mill. In the operating position of the agitating ball mill, therotational axis of the rotor is essentially arranged horizontally.

The separation device is preferably exchangeable. For example, it can bea self-cleaning grading screen or a paddle wheel.

In another advantageous embodiment, the rotor is a hollow rotor withholes arranged radially inside the rotor, and holes arranged radiallyoutside the rotor. During operation, the auxiliary grinding media arehere transported along with a portion of the grinding material flowinside the rotor from a radially inner hole to one of the radially outerholes via the centrifugal action of the rotor, and transported outsidethe rotor with the entire grinding material flow from the radially outerhole to the radially inner hole via the pumping action of the grindingmaterial input opening, so that the auxiliary grinding media circulateinside the agitating ball mill.

The radially inner hole preferably extends in the circumferentialdirection given an inner radius Ri at the rotor, and the radially outerhole preferably extends in the circumferential direction given an outerradius Ra at the rotor. This facilitates the entry of auxiliary grindingmedia along with a portion of the grinding material flow into the rotorcavity, as well as the exit of auxiliary grinding media along with thisportion of grinding material flow out of the rotor cavity.

In a particularly preferred embodiment, the hollow rotor exhibits innerchannels, which each form a fluid connection between a radially innerhole and a radially outer hole. These spoke-like channels arrangedinside the rotor exert a strong centrifugal force on the auxiliarygrinding media, so that the latter are transported back out efficiently.

Other advantages, features and possible applications of the inventionmay be gleaned form the description of an exemplary embodiment based onthe drawing, which is not to be construed as limiting. Shown on:

FIG. 1 is a perspective view of an agitating ball mill according to theinvention in an operating position;

FIG. 2 is a perspective view of the agitating ball mill on FIG. 1 in atilted, non-operating position or maintenance position;

FIG. 3 is a magnified perspective view similar to that of FIG. 2 of theagitating ball mill according to the invention with dismantledseparation device;

FIG. 4 is a perspective view similar to that of FIG. 1 of the agitatingball mill according to the invention;

FIG. 5 is a perspective view of the agitating ball mill on FIG. 4 withopen processing zone;

FIG. 6 is a sectional view of half of an agitator of a respectiveexemplary embodiment of the agitating ball mill according to theinvention, wherein the cutting plane is selected in such a way as toencompass the rotational axis A-A of the agitator;

FIG. 7 is a sectional view of a diagrammatically depicted agitator,whose rotor has inner channels and enables grinding medium circulation.

FIG. 1 shows an agitating ball mill according to the invention in itsoperating position with horizontal rotor rotational axis. The agitatingball mill is secured to a vertical element 2, which is connected with anengine bracket 1. A motor 3 uses a belt transmission 4 to drive a pulley5, which is secured with the rotor 21 (see FIG. 5) of the agitating ballmill so that it cannot rotate via a shaft situated in a bearing 6arranged under a cladding 8 (see FIG. 4). The rotationally driven rotor21 rotates in the grinding chamber 9. The grinding material to be groundpasses through a grinding material input opening 11 arranged radiallyoutside and radially on the grinding chamber 9 and into the grindingchamber 9, and exits the grinding chamber 9 via a grinding materialoutput opening 12 arranged radially inside and axially on the grindingchamber. The grinding chamber essentially consists of three parts,specifically a first, flat grinding chamber wall 13, a curved grindingchamber wall 14 on the grinding chamber periphery, and a second flatgrinding chamber wall 15. The curved grinding chamber wall 14 and thesecond flat grinding chamber wall 15 are rigidly connected with eachother to form a single unit. This unit 14, 15 is coupled to the firstflat grinding chamber wall 13 by means of a hinge 10. In addition, acylindrical screen jacket 16 is rigidly connected with the second flatgrinding chamber wall 15, and arranged centrally on the grinding chamberwall 15, projecting axially to the outside. Located inside this screenjacket 16 is a separation device 18 in the form of a cylindrical gradingscreen (see FIG. 3). The grinding material output opening 12 is formedby an axially running pipe, which ends inside the cylindrical gradingscreen 18. Situated outside the output opening 12 is an inclined,downwardly running groove 17, with which grinding material and grindingmedia can be discharged from the processing zone in a controlledfashion.

FIG. 2 shows the agitating ball mill according to the invention on FIG.1 with a vertical rotational axis of the rotor in the tilted position.The reference numbers and elements corresponding thereto are the same ason FIG. 1. As evident, all function elements 3 to 17 of the agitatingball mill on FIG. 2 are tilted by 90° around a horizontal swivelingaxis. Only the engine bracket 1 and vertical element 2 are in the sameposition as on FIG. 1. In this tilted position, the screen jacket 16 ismore readily accessible, so that, during maintenance, the grading screen18 (see FIG. 3) can be more easily dismantled and installed. Inaddition, auxiliary grinding media (not shown) adhering to the gradingscreen or jammed therein can be easily stripped or shaken into thegrinding chamber 9.

FIG. 3 shows the tilted agitating ball mill according to the inventionas on FIG. 2, but magnified somewhat. The reference numbers and elementscorresponding thereto are the same as on FIG. 1 and FIG. 2. In addition,the grading screen 18 is shown in the dismantled state. As bestillustrated by FIG. 3, the upper cylinder edge of the cylindricalgrading screen 18 has a flange 19 with holes, which is used to securethe grading screen 18 to the screen jacket 16 with screws 20 duringreinstallation. The grading screen 18 could not be dismantled andinstalled in the operating position with horizontal rotational axis ofthe rotor (see FIG. 1) without any preparatory work. The grinding spacecontent and in particular the grinding media would have to be dischargedfirst.

In addition, the tiltability of the agitating ball mill according to theinvention makes it possible to use a separation device other than the“passive” grading screen, e.g., a cellular wheel or a paddle wheel,which can only separate out auxiliary grinding media when operational,i.e., during rotation. If the goal is to stop an agitating ball millequipped with such an, “active” separation device, it can be tilted inthe vertical position with a vertical rotational axis beforehand. Thereverse process is followed during renewed startup. The rotor and“active” separation device are first made to rotate with a verticalrotational axis while the agitating ball mill is still tilted, so thatthe separating action of the “active” separation device is restored,whereupon the agitating ball mill is tilted back into the horizontaloperating position with a horizontal rotational axis.

FIG. 4 shows the agitating ball mill according to the inventionmagnified somewhat by comparison to FIG. 1. The reference numbers andelements corresponding thereto are the same as on FIG. 1, FIG. 2 andFIG. 3. As opposed to FIG. 1, the cladding 8 was here omitted, revealingthe bearing 6 for the drive shaft and carrier 7 of the pivoting enginepart.

FIG. 5 shows the agitating ball mill on FIG. 4 with opened processingzone, i.e., in a state where the grinding chamber 9 is opened. Thegrinding chamber 9 was opened by swiveling the unit 14, 15, 16 comprisedof the second flat grinding chamber wall 15, the curved grinding chamberwall 14 and the screen jacket 16 and coupled to the first flat grindingchamber wall 13 via the hinge 10 away from the grinding chamber wall 13.Visible here is the disk-shaped rotor 21 screwed to the drive shaft sothat it cannot rotate, whose flat surface areas are equipped with pins22, and whose curved edge areas are equipped with additional pins 23along the circumferential direction. Corresponding pins opposing thepins 22 and radially shifted relative thereto are also arranged on thestator surfaces, i.e., on the side of the grinding chamber walls 13 and15 facing into the processing space. The grading screen 18concentrically arranged inside the screen jacket 16 can be discerned inthe middle of the swiveled-away unit 14, 15, 16. One characteristicfeature involves the pins 26, which are also arranged on the rotor disk21, but only on their side facing the grinding chamber wall 15, therebygenerating a cleansing turbulence around a static separation device.These screen cleaning pins, whose length corresponds roughly to thecylinder length of the grading screen, are arranged approximatelyconcentrically around the midpoint of rotor disk 21, and extend parallelto both each other and the rotational axis of the rotor, therebyextending into the gap between the grading screen 18 and screen jacket16 when closing the grinding chamber, i.e., swiveling back the unit 14,15, 16. All elements of the grinding chamber wall, i.e., the first flatgrinding chamber wall 13, the curved grinding chamber wall 14, and thesecond flat grinding chamber wall 15, along with the screen jacket 16,have cooling channels (not shown). The rotor disk 21 incorporates holes27 that unite both processing space halves, and are located in proximityto the connecting points between the screen cleaning pins 26 and rotordisk 21, concentrically around the midpoint of the rotor disk 21.

During operation, the product to be ground (e.g., suspension withparticles to be comminuted) is pumped via the input opening 11 into thegrinding chamber 9, in which the driven rotor disk 21 rotates. Theinteraction between the grinding media (not shown) and the pins 22, 23on the rotor disk 21, as well as the pins 24, 25 on the stator,comminutes the particles suspended in the product. The productcomminuted and dispersed in this way as it passes through the processingspace from the outside in finally arrives at the gap between the gradingscreen 18 and screen jacket 16, and passes through the grading screen 18toward the output opening 12. If, despite the high centrifugal field inthe grinding chamber 9 and its higher density relative to the grindingmaterial, several grinding media get as far as the grading screen owingto “unfortunate” impacts and/or entrainment by the grinding materialflow, they are retained there at the latest. The screen cleaning pins 26circulating relative to the resting grading screen 18 on its surfacewith the rotor speed ensure that the grinding material is vigorouslyswirled with velocity components tangential to the surface of thegrading screen. This keeps the grading screen largely free of depositsand conglutinations. In addition, strays are prevented from accumulatingamong the auxiliary grinding media in the grading screen and quicklyjamming the grading screen together with the grinding material.

FIG. 6 shows a side view of half an agitator of a respective exemplaryembodiment of the agitating ball mill according to the invention,wherein the cutting plane is selected in such a way that the rotationalaxis A-A of the agitator lies therein. The radially inner area of theagitator near the axis was cut away, since its design is largelyindependent for the agitator shown on the figure.

The disk-shaped rotor marked 21 overall is interspersed by axiallyparallel pins 22, which are fitted, screwed or otherwise secured inaxially parallel boreholes of the rotor disk 21, and project into thegrinding chamber from the rotor disk 21 on either of its sides. Inaddition, pins 23 extending radially out are spaced apart from eachother in a circumferential direction on the outer edge of the rotor disk21. The stator or grinding space casing is formed by the first flatgrinding chamber wall 13, the curved grinding chamber wall 14 as well asthe second grinding chamber wall 15 (compare FIG. 5). The two flatgrinding chamber walls 13 and 15 have pins 24 and 25 extending into thegrinding space, which are offset relative to the pins 22 of the rotordisk 21. The radial pins arranged on the outer edge of the rotor disk 21contribute significantly to the overall grinding capacity, since boththese pins 23 as well as the grinding material exhibit particularly highspeeds in this radially outermost area, so that a great deal of energyis expended there between the pins 23 and the grinding material or theauxiliary grinding media. The mentioned grinding chamber walls 13, 14and 15 have claddings 28, 29 and 30 on the grinding space side, whichconsist of a non-abrasive material. Also subjected to a high level ofwear, pins 22, 23, 24 and 25 can ideally be replaced. The side of theflat grinding chamber wall 15 facing the rotational axis A-A has theonly partially shown screen jacket 16, which covers the grading screen18 (compare FIG. 5).

FIG. 7 shows a sectional view of a diagrammatically depicted agitator,whose rotor has inner channels, and enables a grinding mediumcirculation along the sketched-in arrow. To ensure clarity, the pins 22,23, 24 and 25 according to the invention shown on FIG. 6 and FIG. 6[sic] were omitted from FIG. 7. The rotor marked 21 overall has at leastone radially inner hole 21 a at a radial distance Ri from the rotationalaxis A-a, and at least one radially outer hole 21 b at a radial distanceRa from the rotational axis A-A. A flow channel is formed between theseholes 21 a and 21 b via channels 21 c inside the rotor 21. The stator isformed by the grinding chamber walls 13, 14 and 15 (compare FIG. 5).During operation, both drag and inertia forces act on the grinding mediadistributed in the grinding material (shown as black dots). In thegrinding space area between the rotor 21 and the grinding chamber walls13 and 15 forming the start, the grinding media are dragged toward theinside along with the grinding material pumped into the grinding spaceradially from outside through the grinding material input opening 11(compare FIG. 1, FIG. 5) via the channels formed by 13 and 21 or 13 and15, since the drag forces of the grinding material flow directedradially inward on the grinding media are greater than the centrifugalforces of the grinding media directed radially outward on their curvedpaths. Correlations during operation are exactly opposite in thechannels (“centrifugal channels”) 21 c and the rotor 21. The drag forcesdirected outwardly by the grinding material centrifuged radially outwardact on the grinding media in conjunction with the also outwardlydirected centrifugal forces, so that these are dragged radially outward.As a result, grinding media that always get into the radially inner areaof the grinding space are again conveyed out. This prevents grindingmedia from accumulating on the radially inner separation device (notshown), thereby preventing an obstruction of the separation device,excessive wear of the grinding space, and an overheating of the grindingmaterial in the radially inner area of the grinding space.

REFERENCE LIST

-   1 Engine bracket-   2 Vertical element-   3 Motor-   4 Belt transmission-   5 Pulley-   6 Drive shaft bearing-   7 Pivoting engine part carrier-   8 Cladding-   9 Grinding chamber-   10 Hinge-   11 Grinding material input opening-   12 Grinding material output opening-   13 First flat grinding chamber wall-   14 Curved grinding chamber wall on grinding chamber periphery-   15 Second flat grinding chamber wall-   16 Screen jacket-   17 Groove-   18 Separation device, grading screen-   19 Flange-   20 Screws-   21 Rotor, disk-   21 a Radially inner hole-   21 b Radially outer hole-   21 c Channels-   22 Pin on disk plane-   23 Pin on disk edge-   24 Pin on stator-   25 Pin on stator-   26 Screen cleaning pin-   27 Connecting holes-   28 Cladding-   29 Cladding-   30 Cladding

1. An agitating ball mill comprising a grinding chamber containinggrinding media, a stator and a rotor which are arranged in the grindingchamber, an input opening and an output opening for feeding and removinggrinding material to or from the grinding chamber, a grinding mediumseparation device, arranged in the grinding chamber upstream from theoutput opening, used to separate grinding media entrained in thegrinding material from the grinding material before the latter isremoved from the grinding space through the output opening, the rotorbeing shaped like a rotationally symmetrical element, the stator beingformed by an inner surface of the grinding chamber whose shapeessentially compliments the rotor surface, the rotor and the statorhaving pins arranged over their entire respective surface, which extendfrom the respective surface and project into the processing space. 2.The agitating ball mill according to claim 1, wherein the grindingmaterial input opening is arranged in a radially outer area of thegrinding chamber and the grinding material output opening is arranged ina radially inner area of the grinding chamber.
 3. The agitating ballmill according to claim 1, wherein the rotor is essentially shaped likea truncated cone, wherein the grinding material input opening isarranged in the area of the wide truncated cone end, and the grindingmaterial output opening is arranged in the area of the narrow truncatedcone end of the grinding chamber.
 4. The agitating ball mill accordingto claim 1, wherein the is essentially shaped like a double truncatedcone, wherein the grinding material input opening is arranged in thearea of the wide truncated cone end, and the grinding material outputopening is arranged in the area of the narrow truncated cone end of thegrinding chamber.
 5. The agitating ball mill according to claim 1,wherein the rotor is essentially shaped like a disk, wherein thegrinding material input opening is arranged in the radially outerperipheral area, and the grinding material output opening is arranged inthe radially inner axial area of the grinding chamber.
 6. The agitatingball mill according to claim 5, wherein the disk has pins on both itstwo flat disk surfaces.
 7. The agitating ball mill according to claim 1,wherein the grinding chamber with its stator and rotor and a separatordevice can be pivoted into a swiveled position in such a way that theseparation device arrives at a high location, which is higher than mostof the entire grinding chamber volume.
 8. The agitating ball millaccording to claim 7, wherein the swiveled position is a non-operatingposition of the agitating ball mill.
 9. The agitating ball millaccording to claim 7, wherein the rotational axis of the rotor isessentially arranged horizontal in the operating position of theagitating ball mill.
 10. The agitating ball mill according to claim 7,wherein the rotational axis of the rotor is essentially arrangedvertical in the non-operating position.
 11. The agitating ball millaccording to claim 7, wherein most of the grinding chamber volume takesup between 50% and 100% of the entire grinding chamber volume.
 12. Theagitating ball mill according to claim 7, wherein high location of theseparation device is the highest location of the separation deviceachievable via swiveling.
 13. The agitating ball mill according to claim7, wherein the separation device can be replaced.
 14. The agitating ballmill according to one of the claim 7, wherein the separation device is aself-cleaning grading screen.
 15. The agitating ball mill according toclaim 7, wherein the separation device is a paddle wheel.
 16. Theagitating ball mill according to claim 7, wherein the separation deviceis a separating gap.
 17. The agitating ball mill according to claim 2,wherein the rotor is a hollow rotor with at least one hole arrangedradially inside the rotor and at least one hole arranged radiallyoutside the rotor, wherein, during operation, the auxiliary grindingmedia are transported along with a portion of the grinding material flowinside the rotor from a radially inner hole to a radially outer hole viathe centrifugal action of the rotor, and transported outside the rotorwith the entire grinding material flow from the radially outer hole tothe radially inner hole via the pumping action of the grinding materialinput opening, so that the auxiliary grinding media circulate inside theagitating ball mill.
 18. The agitating ball mill according to claim 17,wherein the radially inner holes extend in the circumferential directiongiven an inner radius Ri at the rotor and the radially outer holesextend in the circumferential direction given an outer radius Ra at therotor.
 19. The agitating ball mill according to claim 17, wherein thehollow rotor exhibits inner channels, which each form a flow between atleast one radially inner hole and at least one of the radially outerholes.